This invention relates to the detection and processing of rapidly changing bioelectric or other signals. More particularly, it relates to methods for detecting, processing smoothing signals having rapidly changing amplitudes, such as EMG signals, which may be generated by the tongue or other muscles, and for providing stable and discrete output signals from input signals detected by a detector, such as an intraoral device.
The use of electromyographic (EMG) signals for control of a prosthesis was proposed by Reiter in 1948. In 1958, an actual surface EMG or myoelectrically controlled prosthetic hand was introduced in Russia. EMG signals recorded from remaining agonist and antagonist muscles in the residual limb of a transradial amputee were used. Since the 1960's, the use of myoelectric control of prostheses and orthoses has continued to be studied and successfully implemented. There are now myoelectric prosthetic devices which use surface EMG signals recorded from one or two muscle sites for proportional or digital actuation of one or more functions of an electric powered prosthetic component.
During the late 1960's and early 1970's, electromyographic or myoelectric based control strategies were studied and compared with myomechanical position controllers. The use of surface EMG or myoelectric controllers has been limited by the long integration intervals required to stabilize rapidly fluctuating surface EMG signals. These long integration intervals slow down the responsivity of the controller. A second limitation of myoelectric controllers has been the small number of resolvable discrete control signal levels obtainable (approximately five). Myomechanical position controlling systems have been found to provide a greater number of discrete control levels, as well as more stable control signals.
A myomechanical technique has been developed for use with mid-cervical spinal cord injured individuals using shoulder movement transduction for proportional two-axis control of prosthetic and orthotic systems, including systems employing functional electrical stimulation. Limitations in using shoulder movement transduction for proportional two-axis control of orthotic and neuroprosthetic systems in the high quadriplegic include a) a decrease in the number of discrete control signal levels achievable and a decrease in the stability of the control signals as the level of spinal cord injury become higher, b) control signal interference from motion of the contralateral shoulder, c) instability of reference position due to postural changes and attachment methods of the position transduce, and d) difficulty in concealing the transducer. Recently there has been renewed interest in using processed surface EMG or myoelectric signals as control signals in spinal cord injured individuals in a single dimensional functional electrical stimulation task.
Oral motor and sensory impairments, including dysphagia and dysarthria, can result from many causes including: traumatic brain injury, cerebral palsy, stroke and other diseases of the nervous system such as Parkinson's disease, multiple sclerosis and amyotrophic lateral sclerosis. The occurrence of oral motor and sensory dysfunction increases with age and can result in increased difficulty with communication, decline in nutritional status and, in some cases, aspiration pneumonia. Improved methods for measuring intraoral motor and sensory function are needed.
Electromyographic (EMG) signals from the genioglossus muscle have been previously measured using surface electrodes placed over the skin under the mandible and using surface electrodes mounted to mandibular appliances or splints. With previous intraoral EMG recording techniques, two to four electrodes are used. Electrode wires exit the mouth anteriorly between the upper and lower incisors and hinder approximation of the teeth.
The mounting of two surface electrodes 3 mm in diameter to the palate side of a maxillary splint has been described by Schwarts, et al. Used to stimulate the soft palate, these electrodes were located 1 cm apart, centered to midline, and 2-3 cm posterior to the vibrating line on the soft palate. The methods by which the two electrode wires exited the mouth was not described.
U.S. Pat. No. 5,212,476 invented by Sean R. Maloney describes an intraoral device for detecting EMG signals from the tongue. The Maloney device describes a single splint having a convex side which may be in contact with either the maxillary or mandibular and includes active electrodes mounted on the splint adjacent to the tongue.